The present invention relates to a spectroscopic measurement system that is suitable for a spectrum over a wide wavelength range and, more particularly, to an automatic and continuous spectroscopic measurement system for a spectrum over a wide wavelength range.
Due to the development of optical communication, demand for a spectroscopic measurement system over a wide wavelength range is has been increased to test the characteristics of various optical elements. To provide a spectroscopic measurement over a wide wavelength range, a plurality of diffraction gratings and detectors should be used owing to the limitation of the efficiency characteristics of the diffraction gratings and the wavelength sensitivity characteristics of the detectors. The diffraction gratings normally cannot provide good and uniform diffraction efficiency over the total region of a wide wavelength range. Instead, the diffraction efficiency is reduced at both sides of a specific frequency providing the peak values. Therefore, a wavelength range that is measured with a diffraction grating is limited by the diffraction efficiency characteristics of the diffraction grating. To perform a spectroscopic measurement over a wide wavelength range (.lambda..sub.1 .about..lambda..sub.3), a first diffraction grating showing good efficiency at a shorter wavelength range (.lambda..sub.1 .about..lambda..sub.2) and a second diffraction grating showing good efficiency at a longer wavelength range (.lambda..sub.2 .about..lambda..sub.3) which is adjacent to the shorter wavelength range are needed.
This problem is similar with respect to the detectors. That is, two detectors are needed each showing good wavelength sensitivity at the relevant regions. A first detector showing good wavelength sensitivity at a shorter wavelength region (.lambda..sub.1 .about..lambda..sub.2) and a second detector showing good wavelength sensitivity at a longer wavelength region (.lambda..sub.2 .about..lambda..sub.3) adjacent to the shorter one should be provided.
The conventional spectroscopic measurement system is directed to the spectroscopic measurement at a relatively narrow wavelength region. The conventional system is as follows:
(A) A single diffraction grating and a single detector are used. PA1 (B) Two diffraction gratings are selectively used while a single detector is commonly operated. PA1 (C) A single diffraction grating and two detectors are provided where both detectors are manually switched.
Since the above systems are provided with a single diffraction grating or a single the measurement characteristics are is limited so that it is difficult to enable measurement over a wide wavelength region. Thus, the conventional systems cannot meet with the recent requirements of spectroscopic measurement over a wide wavelength region.